Process for the preparation of a crude-oil composition with a depressed pour point

ABSTRACT

A method of transporting waxy crudes through conduits at reduced friction and preventing wax separation or precipitation so as to inhibit plugging and flow restriction and improve the pour point properties of the crude by adding to such waxy crudes a small amount of a polymeric material containing aliphatic hydrocarbon side chains of at least 14 carbon atoms. This invention relates to decreasing friction loss in flowing waxy crudes through conduits, generally over great distances but also over short distances such as in well fracturing processes and also to improving the pour point of waxy crudes. More particularly, the invention is directed to crude oil compositions comprising a waxy crude oil and fractions thereof and polymers having aliphatic hydrocarbon side chains with at least 14 carbon atoms, so as to reduce the pour point, prevent wax separation and reduce its friction loss due to flow through pipelines over great distances and short distances.

United States Patent [1 1 Choufoer et a1.

[451 Dec. 4,1973

[ PROCESS FOR THE PREPARATION OF A CRUDE-OIL COMPOSITION WITH ADEPRESSED POUR POINT [75] Inventors: Johannes I'I. Chouioer; Willem J.

Van Kerkvoort; Pieter H. Van der Meij; Thomas Schrueder, all ofAmsterdam, Netherlands [30] Foreign Application Priority Data July 7,1967 Netherlands .1 6709453 [52] US. Cl 137/13, 44/62, 44/70, 44/80 [51]Int. Cl Fl7d 1/16, C101 1/18 [58] Field of Search 44/51, 62, 70, 80;137/13 [56] References Cited UNITED STATES PATENTS 3,445,205 5/1969Patinkin et a1 44/62 3,447,915 6/1969 Otto 44/62 3,462,249 8/1969 Tunkel44/62 3,248,186 4/1966 Brownawell et al. 44/62 3,576,639 3/1971 Aaron eta1 44/62 X 3,449,251 6/1969 Tunkel et al 44/62 X FOREIGN PATENTS ORAPPLICATlONS 6,603,483 9/1967 Netherlands 44/62 Primary Examiner-DanielE. Wyman Assistant Examiner-W. J. Shine Attorney-George G. Pritzker andJ. H. McCarthy [57 ABSTRACT A method of transporting waxy crudes throughconduits at reduced friction and preventing wax separation orprecipitation so as to inhibit plugging and flow restriction and improvethe pour point'properties of the crude by adding to such waxy crudes asmall amount of a polymeric material containing aliphatic hydrocarbonside chains of at least 14 carbon atoms.

This invention relates to decreasing friction loss in flowing waxycrudes through conduits, generally over great distances but also overshort distances such as in well fracturing processes and also toimproving the pour point of waxy crudes. More particularly, theinvention is directed to crude oil compositions comprising a waxy crudeoil and fractions thereof and polymers having aliphatic hydrocarbon sidechains with at least 14 carbon atoms, so as to reduce the pour point,prevent wax separation and reduce its friction loss due to flow throughpipelines over great distances and short distances.

6 Claims, No Drawings PROCESS FOR THE PREPARATION OF A CRUDE-OILCOMPOSITION WITH A DEPRESSED' POUR POINT BACKGROUND OF THE INVENTIONDependent on the field of production, crude oils may containconsiderable quantities of wax. This wax gradually separates when theoil is cooled to below a certain temperature. The coherence of theseparated wax crystals in spatial structures imparts a certain stifinessto the oil. At sufficiently low temperatures the oil may even completelysolidify. As will be explained below, the presence of crystallized waxin crude oil has a detrimental effect on the flow properties andhandleability of the oil.

When crude oil is produced from a well which passes through strata oflower temperatures than that of the oil-bearing formation, the oilcoming into contact with the cold wall of the well may stiffen, whichinterferes with its transport to the surface. If production -istemporarily interrupted, the oil may even solidify completely,

which involves serious problems when production is resumed.

When oil is stored in tanks which are not provided with heatingfacilities or insulation, the oil in contact with the cold walls andbottom of the tank will cool down and, as a result, may stiffen. Thisleads to difficulties in pumping the oil from the tank; infact,considerable quantities of stiffened oil may thus remain behind, whichreduces the effective capacity of thetank.

This problem acquires even greater importance during transport of waxycrude oil 'in unheated tankers, where the walls of the compartments arepartly formed by the ships hull, which is in direct contact with thecold sea water. Large quantities of stiffened oil remaining behind whenthe tanker is discharged, reduce the carrying capacity of the ship; inaddition, subsequent cargoes of crude oil may become contaminated.

The poorer flow properties of the oil at lower temper ature will alsoconsiderably interfere with the transport of the oil through a pipeline,either by pumping or by flow under the influence of prevailing pressureor level difi'erences.

When waxy crude oils are pumped through a pipeline, high flowresistances may build up, thus calling for settling, centrifuging,filtration or coalescence, require the'oil to be thin-liquid. If, owingto the presence of crystallized wax, the flow of the oil isinsufficient, there is a possibility that these operations cannot becarried out at all or only to a limited extent.

Good flow properties of a crude oil are desired not only for transportand storage, but also for many other reasons. In this connection, forexample, mention may be made of sampling, the transmittance of pressuresignals through narrow lines and the proper functioning of automaticequipment installed in refineries and along pipelines for purposes suchas temperature and density measurements.

As-appears from the above, the flow properties of a crude oil play agreat part both during production and upon storage, transport andrefining of the oil. It is therefore very important to minimize theadverse effect of wax on the flow properties of the oil.

To predict the flow behaviour of a crude oil under operationalconditions, laboratory-scale measurements are carried out of quantitieswhich may be regarded as characteristic of the flow behaviour of theoil, viz. pour point, viscosity and yield stress. The pour point is acriterion of the lowest permissible temperature during storage ortransport or during a possible interruption of transport. The 'yieldstress gives an impression of the shear stresses which may be expectedif a stagnant oil is to be set in motion again. The viscosity isparticularly related to the resistance which the oil experiences duringpumping.

In general, it may be said that according as a crude oil has a lowerpour point, a lower yield stress and a a very high pump power. This maylead to high cost of transport, particularly in long-distancepipelines.If the resistance is very high, the available discharge pressure of thepump or the maximum permissible pressure determined by the strength ofthe pipe may be insufficient, so that the crude oil cannot be pumped.

If pumping is interrupted while the waxy crude oil is in the pipeline,the oil, which is often warmer than the surroundings, will cool down.The'wax separated during cooling can freely form a spatialstructure,'which may extend over the entire cross section of the pipeand requires a very high pumppressure to be broken. If this pressureexceeds the available or permissible discharge, pressure, transportcannot be resumed.

When a waxy crude is pumped through a pipeline as well as when itremains still, the oil may solidify on the cold pipe wall to form adeposit, which remains behind. This reduces the capacity of the pipelineand entails the risk of contamination of subsequent batches of crude oilwhich have to be pumped through the pipeline.

Certain operations of crude oil refining, such as separation of water orsediment, for example by means of lower viscosity, it will betterhandleable in practice. It. is well known in the 'art that frictionresulting in the transportation of hydrocarbon liquids, ranging inviscosity from gasoline to also waxy crude oils transported throughpipelines, contributes greatly to pumping costs due to increasing energyrequirements necessary to overcome frictional increases due to waxdepositions which can ultimatelyseriously damage the pipelines.

To reduce friction and overcome the undesired effects mentioned above,various means have been tried such as coating of the pipe walls withfriction reducing materials or by addition of friction reducing chemicalagents to the transported liquids such as described in 'U. S. Pat. Nos.2,492,173; 3,023,760; 3,102,548 and 3,215,154. However, these means ofreducing friction have met with little success because of the high costof either coating the pipe walls or that of the friction reducingchemical agents.

SUMMARY OF THE INVENTION It has now been found that the flow propertiesof waxy crude oils can be improved in a simple manner by adding to theoil a small quantity of polymeric compounds with a special structure.For, it has appeared that polymers containing aliphatic hydrocarbon sidechains with at least 14 carbon atoms and which polymers may be regardedas having been obtained by polymerization of olefinically unsaturatedcompounds, are even at a low concentration capable of effecting aconsiderable reduction in pour point, yield stress and viscosity of waxycrude oils. i

The invention therefore relates to a crude oil composition comprising awaxy crude oil and polymers containing aliphatic hydrocarbon side chainswith at least 14 carbon atoms, which polymers may be taken to have beenobtained by polymerization of olefinically unsaturated compounds.

For the sake of brevity the terms "long hydrocarbon chains" and longhydrocarbon side chains will be used hereinafter to designate aliphatichydrocarbon chains and aliphatic hydrocarbon side chains with at least14 carbon atoms, respectively.

As the polymers according to the invention are capable of improving theflow properties of waxycrude oils, the afore-mentioned problems, whicharise during production, storage, transport and refining of waxy crudeoils owing to insufficient flow, can be effectively solved byincorporating these polymers into the waxy crude oil. Some aspects ofthe invention will be further discussed hereinafter.

When waxy crude oil is shipped, it is customary to keep the cargo duringtransport at an elevated temperature, for example by means of steamcoils. The invention offers the possibility of shipping waxycrude oilswithout heating during the voyage being necessary. This means not onlyan appreciable saving for existing tankers, where the availableenergycan then be fully utilized to propel the ship, but particularlywhen constructing new tankers, where the installation of costlyequipment for heating the cargo can be omitted. In spite of the coldshipment a low tum-out loss can be maintained. Shipment of unheated waxycrude oil containing polymers according to the invention permits the useof higher discharge pumping rates.

One of the most serious interruptions which may occur during transportof crude oil through a pipeline is line blocking after pumping at lowtemperatures or after the oil in the line having remained still. Thisrisk is by no means imaginary, particularly when waxy crude oils arepumped. In this connection crude oils to be transported throughpipelines have to meet stringent requirements as regards flowproperties. It was for this reason that in the past various waxy crudeoils were 'rejected for pipeline transport, so that these oils had to betransported in a different way. The present invention, which aims atimproving the flow properties of waxy crude oils, is preeminentlysuitable considerably to reduce any risks during transport of such oils.The invention not only presents the possibility of reducing the requiredpump power, which'will reduce the cost of pumping, but by applying theinvention the transport capacity of the line may be increased at thesame pump power. Waxy crude oils which up to now were regarded asunacceptable for pipeline transport because of their flow properties,can now be rendered suitable for this,

purpose by applying the invention.

In comparison with known techniques to render waxy crude oils suitablefor pipeline transport, which involve dilution of the waxy crude oilwith a relatively large quantity of a thin-liquid oil with a low waxcontent, the present methodhas the advantage that, since only veryresidue. This is an important aspect of the invention, as these residuesare employed, for instance, as fuel oil for heating purposes and as fuelfor low-speed diesel engines. In these applications the flow propertiesplay a very important part.

In order to be suitable for application according to the invention, thepolymers'should contain long hydrocarbon side chains with at least 14carbon atoms. Preferred are polymers wherein the long hydrocarbon sidechains are unbranched and saturated, that is, polymers in which the longhydrocarbon, side chains can be represented by the formula CH (CH ),,CHin which n 2 12. For practical applications, preferably polymers arechosen with long hydrocarbon side chains, wherein the number of carbonatoms is at least 16 and at most 30, in particular at least 18 and atmost The polymers that may be employed as pour point depressantsaccording to the invention consist of a main chain built up of carbonatoms, which main chain carries long hydrocarbon side chains. These longhydrocarbon side chains may be attached either directly or indirectly tothe main chain. In the former case there are no further atoms betweenthe first carbon atom of the long hydrocarbon side chain and the carbonatom of the main chain to which the side chain is attached. If the longhydrocarbon side chain is attached indirectly to the main chain, one ormore other atoms such as carbon, oxygen, sulphur,-nitrogen or phosphorusatoms are present between the first carbon atom of the long hydrocarbonside chain and the carbon atom of the main chain to which the side chainis attached. Preference is given to polymers wherein the longhydrocarbon side chains are attached indirectly to the main chain, viaone or more oxygen and/or carbon atoms. Some examples of polymerswherein the aliphatic hydrocarbon side chains are attached indirectly tothe main chain via one or more oxygen and/or carbon atomsare-polymers-wherein the aliphatic hydrocarbon side chains are attachedto the main chain via a carboxyl group or via an oxygen atom, or via atleast two carbon atoms of an aromatic ring system.

The preparation of such polymers may basically be carried out in twomanners. In the first place, these polymers can be prepared bypolymerization of olefinically unsaturated compounds, of which at leasta proportion consists of olefinically unsaturated compounds containing,in addition to a polymerizable C=C group, a long hydrocarbon chain.Olefinically unsaturated compounds of this type will hereinafter betermed olefinically unsaturated compounds containing a long hydrocarbonchain. A second manner in which these small quantities of polymer arenecessary to re'achthe polymers can be prepared is by polymerization ofolefinically unsaturated compounds containing no long hydrocarbon'chainand aftertreatment of the polymer, by means of which these longhydrocarbon chains are introduced into the polymer as side chains.

The polymers applicable as pour point depressants according to theinvention may be either homopolymers or copolymers.

If the preparation is carried out by direct polymerization, that is,without an after-treatment, the material to be polymerized shouldinvariably contain olefinically unsaturated compounds with longhydrocarbon chains. When homopolymers are prepared in this manner, thestarting material is one specific olefinically unsaturated monomer witha long hydrocarbon chain. When copolymers are prepared in this manner,the starting material is a monomer mixture which, in addition to aspecific olefinically unsaturated monomer with a long hydrocarbon chain,contains one or more other monomers which may or may not contain a longhydrocarbon chain.

If the preparation is carried out by indirect polymerization, i.e.,including an after-treatment, the material to be polymerized need notcontain any olefinically unsaturated compounds with long hydrocarbonchains. When homopolymers are prepared in this manner, the startingmaterial is one specific olefinically unsaturated monomer from which apolymer can be prepared that is suitable for the desiredafter-treatment. When co-" polymers are thus prepared, thestartingmaterial is, for example, a mixture of monomers, which, in addition toone specific monomer from which a polymer can be prepared that issuitable for the desired aftertreatment, contains one or more othermonomers which may or may not contain a long hydrocarbon chain.

The molecular weight of the polymers applicable as flow improvers of theinvention may vary between wide limits. For application in practice itis preferable to choose polymers whose average molecular weight (numberof average M ranges between 1,000 and 1,000,000, in particular between4,000and 100,000.

Depending upon the nature of the parafi'in waxes present in the crudeoil, it may be preferable to incorporate in this crude oil polymers ofthe invention, wherein the long hydrocarbon side chains differ in chainlength by a number of carbon atoms.

Some examples of olefinically unsaturated compounds containing longhydrocarbon chains, suitable for the preparation of the polymersaccording to the invention, are vinyl esters and allyl esters ofsaturated monocarboxylicacids, such as vinyl esters and al'lyl esters ofarachidic acid and behenic acid; alkyl esters of unsaturatedmonocarboxylic acids, such as n-octad'ecyl acrylate and n-eicosylmethacrylate alkyl amides of unsaturated monocarboxylic acids such asn-eicosyl acrylamide and n-docosyl methacrylamide; dialkyl esters ofunsaturated dicarboxylic acids, such as di-noctadecyl maleate anddi-n-tetracosyl fumarate; dialkylamides of unsaturated dicarboxylicacids, such as din-eicosylmaleic diamide and di-n-docosylfumaricdiamide; imides of unsaturated dicarboxylic acids, such asn-octadecylmaleic acid imide and n-eicosylmaleic acid imide; alkyl vinylethers,.such as n-docosylvinyl ether and n-tetracosyl vinyl ether andmono-olefins such as l-octacosene and l-docosene and olefinicallyunsaturated aromatic compounds, such as alkylstyrenes, acylstyrenes,alkylhydroxystyrenes, alkylcarboxystyrenes, alkyloxystyrenes,alkylamidostyrenes, alkylvinylnaphthalenes and acylvinylnaphthalenes.

Some examples of olefinically unsaturated compounds which have no longhydrocarbon chains and by means of which the compounds which do possesssuch long hydrocarbon chains can be copolymerized are, for instance,vinyl esters of unsaturated monocarboxylic acids, such as vinyl acetate;alkyl esters of unsaturated mono and dicarboxylic acids, such as methylmethacrylate and diethyl maleate, alkyl vinyl ethers, such as octylvinyl ether; mono-oletms, such as ethane and isobutene and aromaticcompounds, such as styrene, a-methylstyrene and vinylnaphthalene.

Some examples of polymers'obtained by direct polymerization ofolefinically unsaturated compounds of which at least a proportionconsists of olefinically unsaturated compounds with long hydrocarbonchains, are, for instance:

Copolymers of vinyl esters of saturated monocarboxylic acids with oneanother.

Copolymers of vinyl esters of saturated monocarboxylic acids withmono-olefins.

Copolymers of allyl esters of saturated monocarboxylic acids with'oneanother.

l-lomopolymers of alkyl esters of unsaturated monocarboxylic acids.

Copolymers of alkyl esters of unsaturated monocarboxylic acids with oneanother.

Copolymers of alkyl esters of unsaturated monocarboxylic acids withdialkyl esters of unsaturated dicarboxylic acids or with mono-olefins.

l-lomopolymers of dialkyl esters of unsaturated dicarboxylic acids.

Copolymers of dialkyl esters of unsaturated dicarboxylic acids withmono-olefins.

Homopolymers of alkyl vinyl ethers.

Copolymers of alkyl vinyl ethers with one another.

' If the polymers are copolymers they may be built up either of two orof more than two different monomers.

Some examples of terpolymers are, for instance, terpolymers obtained bycopolymerization of a vinyl ester of a saturated monocarboxylic acidwith a dialkyl ester of an unsaturated dicarboxylic acid and amono-olefin or an alkyl ester of an unsaturated monocarboxylic acid.

Some examples of polymet9 tained by polymerization of olefinicallyunsaturated compounds containing no long hydrocarbon chains and where,by aftertreatment of the polymer, long hydrocarbon chains are introducedinto the polymer as side chains, are, for example: a a

Copolymers of unsaturated monocarboxylic acids, dicarboxylic acids ofanhydrides thereof with monoolefins,'vinyl esters of saturatedmonocarboxylic acids of dialkyl esters of unsaturated dicarboxylicacids, which polymers have been "after-treated with an aliphatic alcoholcontaining a long hydrocarbon chain.

Homopolymers of unsaturated alcohols; which polymers have beenafter-treated with an aliphatic carboxylic acid or aliphatic carboxylicchloride containing a long hydrocarbon chain.

Homopolymers of alkyl esters of unsaturated monocarboxylic acids orcopolymers of alkyl esters of unsaturated monocarboxylic acids with oneanother or with monolefins, which polymers have been after-treated withan aliphatic amine containing a long hydrocarbon chain.

Copolymers of anhydrides of unsaturated dicarboxylic acids withmono-olefins or other olefinically unsaturated compounds, which polymershave been aftertreated with an aliphatic amine containing a longhydrocarbon chain.

Homopolymers and copolymers of styrene and substituted styrenes, intowhich polymers long hydrocarbon chains have been introduced as sidechains by means of alkylation or acylation.

Although polymers which contain aliphatic hydrocarbon side chains withat least 14 carbon atoms and which may be taken to have been obtained bypolymerization of olefinically unsaturated compounds, are in 7 generalsuitable for improving the flow properties of waxy crude oils,preference is given to polymers which may be taken to have been obtainedby polymerization of olefinically unsaturated compounds which consist atleast partly of olefinically unsaturated aliphatic compounds containinga saturated hydrocarbon chain with at least 14 carbon atoms.

Favourable results can be obtained by the application of the polymersmentioned below.

Homoor copolymers of alkyl esters of unsaturated carboxylic acids, suchas homoor copolymers of alkyl esters of unsaturated monocarboxylicacids, in particular homoor copolymers of alkyl acrylates. Examples ofvery suitable homopolymers of alkyl 'acrylates are homopolymers ofn-tetradecyl acrylate, homopolymers of n-hexadecyl acrylate,homopolymers of n-octadecyl acrylate and homopolymers of n-eicosylacrylate.

I Homoor copolymers of alkyl vinyl ethers, in particular homopolymers ofn-octadecyl vinyl ether.

Copolymers of a mono-olefin and a dialkyl ester of an unsaturateddicarboxylic acid with at least. 14 carbon atoms in the alkyl groups, inparticular'copolymers of ethylene and di-n-octadecyl maleate.

Homoor copolymers of vinylesters of saturated monocarboxylic acids, inparticular copolymers of vinyl esters of hydrogenated rape-seed oilfattyacids.

Preference is given to homoor copolymers of alkyl esters of unsaturatedcarboxylic acids, such as homoor copolymers of alkyl esters ofunsaturated monocarboxylic acids, in particular homoor copolymers ofalkyl acrylates. Most preferred are homoor copolymers of alkyl acrylateshaving 18 to 26 carbon atoms in the alkyl group, in particular ahomopolymer of noctadecyl acrylate and a homopolymer of n-eicosylacrylate. 3

The concentration in which the polymers may be applied may vary betweenwide limits', depending upon the nature, the structure and the molecularweight of the polymer to be employed, the nature of and the quantity ofthe paraffin waxes present in the crude oil, and the improvement of theflow properties envisaged.

In some instances, a quantity of 0.001 percent w, calculated on thecrude oil composition, is already sufficient for attaining the desiredimprovement in flow properties. in mostcases, a quantity of 2.0percentgw is amply sufficient.

Preferably, from 0.002 percent w to 0.2 percent w of the polymers isincorporated into the crude oil.

The present polymers have so far been designated in the specification asflow improvers of waxycrude oils. Their features include properties toreduce the pour point, the viscosity and the yield stress of waxy crudeoils. With regard to each of these properties: separately they can, ifdesired, also be designated as pour point depressants, viscositydepressants and yield stress depressants. In this connection it shouldbe observed that a compound may in general be regarded as belonging tothe class of pour point depressants only if it is capable of effecting apour point reduction of at least 6C when it is applied in aconcentration of at most 0.2 percent w.

The waxy crude oil to which the polymers according The present polymers,which are particularly important as additives to ease the transport ofwaxy crude oils through pipelines, by tankers or by other means, canalso be very suitably used in oil wells producing waxy crude to preventthe-formation of waxy deposits or to dissolve such deposits formed onthe walls of the well.

PREFERRED EMBODIMENT OF THE INVENTION The invention will now be furtherelucidated with the aid of the following examples.

Seven polymers of the invention have been applied in various differentconcentrations in the following six crude oils.

Crude Oil I Crude Oil 11 A crude oil originating from South America,with a kinematic viscosity of 1.82 cS at C, a wax content of 17.5percent w (setting point of the wax 54.5C), a pour point of 26C,determined according to method A, and a pour 'point'of 29C, determinedaccording to method C.

Crude Oil III A crude oil originating from North Africa, with akinematic viscosity of 5.13 cS at 37.8C, a wax content of 7.0 percentw'(setting point, of the wax 58.0C), a pour point of 4C, determinedaccording to method A, and a pour point of +2C, determined according tomethod Crude on [V A crude oil originating from North Africa, with akinematic viscosity of 3.66 cS at 37.8C, a wax content of 7.8 percent w(setting point of the wax 51.5C), a pour point of +2C, determinedaccording to method A, and a pour point of +5C, determined according tomethod Crude Oil Vv A crude oil originating from West Africa, with akinematic viscosity of 15.0 cS at 50C, a wax content of 17.8 percent w(setting point of the wax 56.0C), a pour point of 20C, determinedaccording to method B, and a pour point of 32C, determined according tomethod D.

Crude Oil VI A crude oil originating from West Africa, with a kinematicviscosity of 2.70 cS at 50C, a wax content of 7.0

to the invention may be added, may consist of one waxy percent w(setting point of the wax 54.0C), a pour point of 1 1C, determinedaccording to method A, and a pour point of 14C, determined according tomethod As regards the methods for the determination of the pour point ofwaxy crude oils, the following should be pointed out in addition.

The pour point of a waxy crude oil is often dependent upon the thermalpre-treatment to which the oil has been subjected.

On the basis of whether or not a thermal pretreatment is carried out,the methods suitable for the determination of the pour point of waxycrude oils may be divided into two groups, viz.:

1. methods where the pour point is determined on a sample that is notreheated before the determination;

2. methods where the sample is heated to 46C just before thedetermination.

Although the thermal treatment in some instances results in a higherpour point, it is perhaps less realistic, as the pertaining crude oil isnot subjected to this thermal cycle in actual practice.

From the examples in this patent application it appears that thepolymers of the invention are capable of depressing the pour point in ageneral sense, i.e., independent of whether or not the thermalpre-treatment is carried out.

The pour point determination methods A, B, C, and D, mentioned in theexamples, were carried out as follows.

METHOD A Two samples of a crude oil are heated to 65C, at whichtemperature the desired quantity of polymer is added to one of thesamples. After cooling the samples to room temperature the pour point isdetermined as described in ASTM D 97-66/IP /67, but without thereheating to 46C.

METHOD B As described under method A, but in its first line read 100Cinstead of 65C.

METHOD C Two samples of a crude oil are heated to 65C, at whichtemperature the desired quantity of polymer is added to one of thesamples. After cooling to room temperature the samples are stored atroom temperature for at least 24 hours. Subsequently, the pour point isdetermined as described in ASTM D 97-66/IP 15/67. This pour point isusually specified as the ASTM maximum pour point or the 1? maximum pourpoint.

METHOD D I As described under method C, but in its first line read 100Cinstead cf 65C.

The results of the experiments are given in Table I, in which the numberof degrees Centigrade is specified at which the pour point determinedaccording to any one of methods A-D is depressed after addition of thevarious polymers.

For comparison two related polymers (a poly-n-C alkyl methacrylate and apoly n-C alkyl methacrylate) were tested as pour point depressants incrude oil III.

The results of these experiments (with polymers outside the scope of thepresent invention) are also incorporated in Table I.

YIELD STRESS A sample of crude oil is heated to 65C, at whichtemperature the desired quantity of polymer is added to the sample.After cooling to room temperature a metal U-tube with a length of 54 cmand an inside diameter of 3.8 mm is filled with the oil to be tested.Subsequently, the oil in the tube is cooled down to the de;

termination temperature, after which the pressure on one of the U-tubelimbs is gradually raised.

The pressure (P,,) at which the first flow is observed is used forcalculating the yield stress. The yield stress (defined as the shearstress required for setting a congealed oil into motion) is calculatedfrom the observed P with the aid of the equation:

7 P D/4 L,

where:

1', yield stress, dyn/cm 7 P pressure at which the first flow isobserved,

D diameter of the tube, cm

L length of the tube, cm

The yield stress of a sample of crude oil VI to which 0.005 percent w ofpoly n-C alkyl acrylate had been added was determined at two differenttemperatures in the manner described above, and was compared with theyield stress of a sample of crude oil VI which had been subjected to asimilar thermal pre-treatment without any additive. The results obtainedare given below: Crude oil VI:

yield stress at 8C: 302 dyn/cm Crude oil VI 0.005 percent w of poly-n-Calkyl acrylate:

yield stress at 8C: 10 dyn/cm .yisli trss at C= 17 i Behaviour DuringDistillation a maximum vapourtemperature of 300C) from the untreatedcrude oil and from the two crude oil samples towhich polymer had beenadded.

The residues showed the following pour points (determined according toASTM D 97-66).

Residue from untreated crude oil Vl maximum pour point 38C minimum pourpoint 35C Residue from crude oil VI 0.03%w of poly-n-C alkyl acrylateResidue from crude oil VI 0.03%w of poly-n-C alkyl acrylate maximum pourpoint 32C minimum pour point l7C maximum pour point 23C minimum pourpoint l7C VISCOSITY Since waxy crude oils at lower temperatures behaveas non-Newtonian liquids, the viscosity of such oils can be determinedin a realistic manner only in a viscometer wherein either the shearingstress or the rate of shear can be adjusted between narrow limits and bekept constant. Very suitable for determining viscosities of waxy crudeoils is the Ferranti Portable Viscometer, Model VL, a so-called Couettecoaxial-cylindrical viscometer of the constant-shear-rate type.

A sample of crude oil is heated to C, at which temperature the desiredquantity of polymer is added to the sample. After cooling down to roomtemperature the reservoir of the viscometer is filled with the oil to betested.

Note: The yield stress and viscosity (Ferranti viscometer) values forcrude oil VII mentioned in this patent application were determined asdescribed on pages 15 and 17 for crude oil VI, but without heating to65C.

PROPERTIES OF THE DOPED OIL Actual pour point: 2C.

b. Yield stress Test temperature Yield stress c. Viscosity (Ferrantiviscometer) rate of a... -s shear.

test sec" 36.9 164 628 temperatue, C 21.4 56 c? 34 cP 32 cP 18.3 82 c?46 cl 37 c? 15.5 110 cl 52 c? 41 0P 9.7 159 c? 69 CP 47 c? 5.2 223P s7cP 47 of When the cargo was loaded in North Africa for the 1st voyage,threesamples of crude oil VII were taken.

Two of these samples were doped with polymers according to theinvention; the third sample was not doped. The samples were kept indeward, which were stored during the voyage in an insulated wooden case.On arrival in West Europe the samples were stored in a space at atemperature of about 13C. After being stored for about 1 week the yieldstress and viscosity of the samples were determined. The results aregiven below. 1

Sample I: crude oil VII.

Sample 2: crude oil VII 1 0.02 percent w poly-n-C alkyl acrylate.

On arrival of the tanker in West Europe restart trials were made withthe doped and the undoped'crude oil in a pipe circuit consisting of2,000-m 20inch noninsulated pipe and 2,000 m 24 inch insulated pipe. Thetrials were performed as follows.

The oil undertest was pumped at itstemperature of arrival into thecircuit, after which the pump was stopped for some days (shut-in time),so that the oil was allowed to cool down. Subsequently the pressure atthe inlet of the circuit was raised by means of a pump in steps untilthe oil began to flow. The yield stress was calculated from the highestpressure drop over the noninsulated (i.e., cooled) pipe section by meansof the afore-mentioned formula:

The results of the restart trials are mentioned below.

Restart Trials with Undoped and Doped Druce undoped doped crude crudeShut-in time, h 78 102 Average temperature non-insulated pipe. "C 9 3Ambient temperature, C 4 0 Pressure drop in non-insulated pipe,kgf/cm'6.3 0.7S Yield stress related to pipe wall, dyn/cm' 400 47 2ndVoyage 20,000 tons of unheated doped crude oil VII and $30,000 tonsofunheated undoped crude oil VII.

The flow improver used was 0.015 percent w poly-n-C alkyl acrylate.

Temperature during loading in North Africa; 102F Temperature of oiargb'"on arrival in West Europe:

78E. Average rate of cooling: 3F per day.

PROPERTIES OF THE UNDOPED OIL a. Actual pour point: 20C. b. Yield stressTest temperature Yield stress C dyn/cm l7.l' I I8 13.6 302 1 10.4 415c.-,Viscosity (Ferranti viscometer) rate of shear, test sec 36.9 164 328temperature, "C 15.0 192 cP 22.7 114 cP 57 GP 45 cP PROPERTIES OF THEDOPED OIL a. Actual pour point: 2C. b. Yield stress Test temperatureYield stress dyn/cm 6.0' 37 L4 76 3.l 206 .c. ViscosityKFerrantiviscometer) rate of shear, test sec" 36.9 164 328 temperature, CC V 22.737 cl 30 c? 29 cP 10.2 13161 81 cP CE 4.8 210 CP 119 cP 93 cP It wasfound that the rate of discharge of the doped oil from the tanker was 15percent higher than that of the undoped oil.

After discharge of the undopedoil stored on arrival in West Europe inunheated floating-roof tanks a solid wax-oil mixture re'mained'behind onthe tank wall. This -was not the case with the undoped oil.

The foregoing description of the invention is merely intended to beexplanatory thereof. Various changes in g the details of the describedmethod maybe made,

within the scope of the appended claims, without departing from thespirit of the invention.

We claim as our invention:

1. A composition of matter having improved flow and friction-reducingproperties comprising 1 a major amount of waxy crude oil havingincorporated therein from 0.001 to 2 percent of an oil-soluble polymercontaining aliphatic hydrocarbon side chains having the formulaCH,-(Cl-l,),,-CH where n is an integer of from 14 to 30, said polymerhaving a molecular weight of from 1,000 to 1,000,000 and being a memberselected from the group consisting of (a) homopolymers of alkyl vinylethers or copolymers of alkyl vinyl ethers with one another and (b)copolymers of a mono-olefin and a dialkyl ester of an unsaturateddicarboxylic acid.

2. Composition of claim 1 in which the polymer is obtained byhomopolymerization of an alkyl vinyl ether containing an aliphatichydrocarbon chain or from 14 carbon atoms.

3. Composition of claim 2 in whichthe homoglymei;

is n-octadecyl vinyl ether.

4. Composition of claim 1 in which the polymer is obtained bycopolymerization of a mono-olefin with a dialkyl ester of an unsaturateddicarboxylic acid, which ester contains aliphatic hydrocarbon chains orfrom 14 to 30 carbon atoms in the parts of the molecule derived from thealcohol.

5. Composition of claim 4 in which the copolymer is a copolymer ofethylene and di-n-octadecyl maleate.

6. A method of transporting waxy crude oil through a pipeline underreduced friction and without causing plugging of the pipeline comprisingadding to the waxy crude oil from 0.001 to 2 percent of an oil-solublepolymer containing aliphatic hydrocarbon side chains having the formulaCH -(CH ),,Cl-l where n is an integer of from 14 to 30; said polymerhaving a molecular weight of from 1,000 to 1,000,000 and being a memberselected from the group consisting of (a) homopolymers of alkyl vinylethers or copolymers of alkyl vinyl ethers with one another and (b)copolymers of a monoolefin and a dialkyl ester of an unsaturateddicarboxylic acid.

2. Composition of claim 1 in which the polymer is obtained byhomopolymerization of an alkyl vinyl ether containing an aliphatichydrocarbon chain or from 14 carbon atoms.
 3. Composition of claim 2 inwhich the homopolymer is n-octadecyl vinyl ether.
 4. Composition ofclaim 1 in which the polymer is obtained by copolymerization of amono-olefin with a dialkyl ester of an unsaturated dicarboxylic acid,which ester contains aliphatic hydrocarbon chains or from 14 to 30carbon atoms in the parts of the molecule derived from the alcohol. 5.Composition of claim 4 in which the copolymer is a copolymer of ethyleneand di-n-octadecyl maleate.
 6. A method of transporting waxy crude oilthrough a pipeline under reduced friction and without causing pluggingof the pipeline comprising adding to the waxy crude oil from 0.001 to 2percent of an oil-soluble polymer containing aliphatic hydrocarbon sidechains having the formula CH3-(CH2)n-CH2- where n is an integer of from14 to 30, said polymer having a molecular weight of from 1,000 to1,000,000 and being a member selected from the group consisting of (a)homopolymers of alkyl vinyl ethers or copolymers of alkyl vinyl etherswith one another and (b) copolymers of a mono-olefin and a dialkyl esterof an unsaturated dicarboxylic acid.